Camshaft adjusting devices, especially those that operate hydraulically, have been known for a long time in the prior art. In hydraulic camshaft adjusters, an impeller is provided in which vanes are formed or arranged. The vanes are located in hydraulic chambers that are formed in an outer rotor (usually called a stator). Through corresponding pressurization of respective sides of the hydraulic chambers with hydraulic fluid, the inner rotor (connected to the camshaft) is adjusted relative to the stator between an “advanced stop” and a “retarded stop.”
Here, the flow of hydraulic oil is controlled by a control valve that is constructed according to the class and as an electrically controlled directional control valve. Such a control valve is disclosed in DE 10 2008 004 591 A1.
In such a control valve it is provided that pressure oil is guided from a high-pressure area through a fluid line formed by at least one borehole in the control valve in an area of the valve facing the camshaft into the interior of the valve. The valve has control elements with which the pressure oil can be fed in a controlled manner into two fluid lines in the axial middle area of the valve, wherein these fluid lines are in fluid connection with the hydraulic chambers of the camshaft adjuster. Through the corresponding flow of hydraulic oil into the hydraulic chambers, the relative rotation of the stator of the camshaft adjuster relative to the camshaft can be performed, which has been known for a long time. The oil is then fed back into a tank in an area of the valve facing away from the camshaft.
The previously noted DE 10 2008 004 591 A1 here provides that the oil is fed in the interior of the control valve and especially through the interior of the control piston (valve piston) and is discharged in the axial end area of the control piston through piston hollow space openings concentrically from the valve. In other words, the oil outflow to the tank is realized in the axial direction through the control valve constructed as a central valve.
A disadvantage in this solution is that, the rotor tappet of an electromagnetic actuator (central magnet) is arranged in the area of the outflow of the hydraulic oil, wherein this tappet contacts the control piston and moves in the axial direction in the necessary manner, in order to control the flow of hydraulic oil in the camshaft adjuster. This configuration allows contaminants (particles) in the oil to reach the contact position between the rotor tappet and the valve piston and to accumulate at this position and thus to subject this wear-sensitive location to abrasive particles. The result is correspondingly disadvantageous wear at the contact position.
It is also a disadvantage that, in some areas, higher temperatures occur in the camshaft adjuster in the area of the central magnet when the internal combustion engine is operating.